Technical Field
The present disclosure relates to a variable filter circuit and a wireless communication apparatus including the variable filter circuit.
Background Art
Conventional variable filter circuits have been given ladder configurations, in which basic circuits are configured by connecting variable capacitances in parallel or in series to resonators such as SAW resonators or BAW resonators and such basic circuits are then combined in multiple stages (see Patent Document 1, for example). In a variable filter circuit, an anti-resonant frequency of each basic circuit is adjusted by controlling the variable capacitance connected in parallel to the resonator, and a resonant frequency of each basic circuit is adjusted by controlling both the variable capacitance connected in parallel and the variable capacitance connected in series to each resonator. A desired band can be set as a pass band as a result.
Patent Document 1: Japanese Patent No. 4053504